The present invention relates to the field of data transmission and storage systems and particularly to redundant data transmission and storage systems which provide high reliability when connected in networks.
Networks are employed, for example, in telephone systems in which subscriber sets are connected together through one or more switching exchanges. In a similar manner, computers and other data processing machines are also connected together to transfer data through networks. Users of such networks require high reliability.
An example of one particular network requiring high reliability is a telephone message metering system which is employed for recording information resulting from toll, long distance and other types of telephone service. Such equipment requires the ability to detect, transmit and store information to enable usage-sensitive charging of subscribers. High reliability is required to insure that subscribers are properly charged. Local service by subscribers has generally been on a non-usage-sensitive basis and has employed equipment which has not been readily adapted for reliable metering on a usage-sensitive basis. With the advent of new types of local telephone usage such as credit-card checking, time-sharing data transmission, and burgulary prevention, a need for reliable detecting, transmitting and storing of information concerning the nature of local usage has become important.
When message metering information is to be transmitted through a network, for example, from a remote to a central telephone office, high reliability in the data transmission must still be maintained.
While the use of redundancy is well-known for improving the reliability of many data transmission and storage systems, a need still exists for providing improved reliability in data transmission systems connected in networks.